SPECIFICITY OF CHANGES IN PROTEASOME PROPERTIES IN DIETHYLMALEATE-INDUCED K562 CELLS
A. S. Tsimokha,1, * A. G. Mittenberg,1 V. A. Kulichkova,1
I. N. Evteeva,1 Yu. Ya. Vatazhok,1 T. N. Moiseeva,1 Yu. B. Ermolaeva,1
E. S. Vashukova,1 I. V. Volkova,1 I. V. Kojukharova,1 L. N. Gause,2
I. M. Konstantinova 1
1 Institute of Cytology RAS, St. Petersburg, and
2 Koltsov Institute of Development Biology RAS, Moscow;
* e-mail: atsimokha@mail.cytspb.rssi.ru
The participation of proteasome in the programmed cells death is now extensively investigated. Studies using
selective inhibitors of proteasomes have provided a direct evidence of both pro- and anti-apoptotic functions of
proteasomes. Such opposite roles of 26S proteasomes in regulation of apoptosis may be defined by the proliferative
state of cell. The induction of apoptosis in K562 cells by diethylmaleate was used as a model to investigate
changes in the subunit composition, phosphorylation state and enzymatic activities of 26S proteasomes undergoing
the programmed cell death. Here we have shown that proteasomes isolated from the cytoplasm of control and
diethylmaleate treated K562 cells differ in their subunit patterns, as well as in the phosphorylation state of
subunits on threonine and tyrosine residues. It has been shown for the first time that proteolytic activity of
26S proteasomes is decreased, and endoribonuclease activity of 26S proteasomes is affected under diethylmaleate
action on K562 cells. Treatment of K562 cells with an inductor of apoptosis - diethylmaleate - leads to
modification of a proteasomal subunit (zeta/α5) associated with RNase activity of proteasomes. These data
suggest the subunit composition and enzymatic activities of 26S proteasomes to be changed in K562 cells undergoing
apoptosis, and that specific subtypes of 26S proteasomes participate in execution of programmed death of these
cells.
Key words: apoptosis, diethylmaleate, K562 cells, mRNA stability, phosphorylation, proteasomes,
ribonucleases, threonine, tyrosine
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